Marine Energy Basics
Marine energy—power generated from ocean waves, currents, tides, and temperature changes—is the world's largest untapped renewable energy resource.
Oceans cover more than 70% of the planet's surface and hold about 97% of the Earth's water. They also hold great potential as a plentiful renewable and reliable energy resource.
What Is Marine Energy?
Nearly 40% of the U.S. population lives in coastal communities where a vast, reliable, and renewable energy source is in constant motion offshore: the ocean. Waves crash against coastlines, tides ebb and flow, and currents churn millions of miles of water. Each form of ocean movement can be converted into electricity.
There's far more energy surging through our country's waves, tides, and currents than we could harness and convert into electricity. But if we tapped all the marine energy we can access, that power would equate to almost 60% of the United States' annual electricity needs. For example, tidal energy in Alaska's Cook Inlet could power the entire state. Waves could provide energy for coastal communities, remote islands, underwater robots, or offshore work, such as marine research, fishing, or military operations. And currents—both fast and slow—could provide clean electricity in isolated areas far offshore or deep beneath the ocean's surface.
Is Marine Energy the Same as Ocean Power?
Not necessarily. Marine energy can be created in the ocean but also in rivers, lakes, streams, estuaries, and more. Marine energy means energy generated from:
- Waves, tides, and currents in oceans, estuaries, and tidal areas
- Free flowing water in rivers, lakes, streams, and man-made channels
- Changes in salinity (salt levels) or pressure
- Changes in water temperature.
How Can We Make Energy From Moving Water?
Unlike rivers, which mostly move in one direction, oceans heave up and down, surge back and forth, and even swirl in circles. These chaotic movements can be challenging to harness, and there are hundreds of technological designs vying for commercial success in the marine energy industry (such as highly flexible devices that can stretch, twist, and bend or ones that can change shape to allow destructive waves to flow through). Some use buoys that bob up and down, sway back and forth, and pitch side to side in waves. Others use underwater turbines that spin in fast-moving currents and tides, like those that surge in and out of Alaska's Cook Inlet.
All marine energy technology must overcome one major challenge: potentially corrosive and destructive oceans and rivers. Devices must withstand turbulent and harsh conditions. The ocean can move with more power than any wind, and salt water and shifting sediments, such as sand, can damage devices. Plus, the marine energy industry has the great responsibility of protecting and preserving marine ecosystems.
How Could Marine Energy Help Us?
Marine energy is both predictable and dependable. The ocean is always moving, making it an ideal member of the renewable energy team. As a bonus, at night when the sun sets and winds tend to slow, as well as during seasonal dips in solar energy and wind energy, marine energy is often at its most powerful.
Marine energy could also contribute to a carbon-pollution-free power sector in an environmentally just and sustainable way. Wave-powered devices can provide fresh water to remote communities or for disaster recovery. It can power offshore jobs, such as those in the fishing industry. And it can be a local and more affordable energy source for coastal and remote communities, many of which rely on expensive fossil fuel shipments that don't always make it. Violent storms can delay or even prevent the fuel from reaching its destination, leaving communities in the dark. But if oceans or rivers flow nearby, marine energy could light up their homes, schools, and businesses all year long.
For more information about ocean energy, browse the following resources.
Marine Energy Technology Glossary
U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy
Marine Energy Fact Sheet, U.S. Department of Energy's Water Power Technologies Office (2021)
Marine Energy in the United States: An Overview of Opportunities, NREL Technical Report (2021)
Marine Energy Stories
Read more stories about how marine energy can help communities take charge of their energy production, generate pollution-free electricity, and support a healthy planet.